How do we get rid of a musty odor in our NC condo near the water?

Not an easy answer. You have to find the cause, starting at the foundation, peeling back carpeting, looking for gaps in concrete, opening in finished walls in basement, doing a moisture test. Cut a square of heavy plastic about 20" wide and tape to the bare concrete floor with duct tape. Check it in 48 hours for how much water is under it. If it is more than a few drops, then you have seepage through the concrete. There are clear sealers that apply with a paint roller that will help a little, but basically the problem has to be tackled from the outside, and that means excavating all around.
Then there's dampness from the roof... generally visible.
If you just have mustiness from not using the place often and it's closed up, then air it out and use natural scents and candles to clear the air. Drape everything with sheets when you leave and wash and bleach them when you get back.

You mean the condo that was under water last week?